Improvement in pressure-gages



ZHShee-ts--SheefL G. H. cR0sBY.`

Pressure Gages.

NO. 345,726. Patented Dec. 23,1873. /'v'yl Wlfle/essa# j Invek/Zr W v 'off w 2 Sheets-Sheet 2.

(i. H. CROSBY. Pressure Gages. N0l 145,726l Patented Dec.23,l873.

UNITED STATES PATENT OFFICE.

GEORGE H. CROSBY, OF EAST SOMERVILLE, MASSACHUSETTS.

,IMPROVEMENT IN PRESSURE-GAGES.

Specification forming part of Letters Patent No. 145,726, dated December23, 1873; application iiled August 6, 1873.

To all whom it may concern:

Y Be it known that I, GEORGE H. CROSBY, of East Somerville, Middlesexcounty, Massachusetts, have invented certain new and useful Improvementsin Vacuum or Pressure Gages, of which the following is a specication:

My invention relates to gages in which the Bourdon tube is used as themeans of giving movement to the index 5 and it consists of a newmechanism for connecting and transmitting the motion of the arm or armsof the Bourdon tub'e to the rack, or equivalent device, for revolvingthe pinion-shaft that carries the pointer or index, the object I have inView being to utilize, as fully as possible, the upward or vertical, aswell as the horizontal, movement of said tube or tubes, thereby throwingits pointer around the graduated dial with the application of lesspressure, and consequently with less danger of injuring the tube. I amthus enabled to use a stouter tube for the same pressure-than would bethe case were I to avail myself of `what I have termed the horizontalmovement of the tube in contradistinction to the upward or verticalmovement of its free end, due to the expansion or straightening out ofthe tube.

To accomplish this result, I employ two links, connected or joinedtogether at one end, and separately pivoted at their opposite ends,which are spread apart in such manner that the two links constitute thesides of a triangle, of which the point where they are joined orconnected together is the apex, and the line drawn between theirseparately-pivoted ends is the base. In case two Bourdon-tube arms orbranches are employed, then one of said links is pivoted to the end ofone of the branches, and the other link is pivoted to. the other branch.In case but one branch or arm is used, then one of the links is pivotedto the end of this branch, and the end of the other link is pivoted tothe case of the gage. Vith the two links is connected the rack orsegment that actuates the index-shaft. In case any portion of theindex-shaft-actuating mechanism is pivoted to the case of the gage,then, where two Bourdon tubes are employed, the links should beconnected with such pivoted portion of the mechanism by a connecting-rodjointed at one end to the apex or point of junction of the links, and atthe other end to said pivoted portion of the mechanism; but, in casethere is no such direct connection with the case of the gage, thejointed intermediate connecting-rod may be dispensed with, the object ofthis arrangement being both to utilize the two movements of each branch,and also to enable each branch to do its own portion of the workindependently of and without interference with the other branch. Withthe transmitting mechanism intermediate between the Bourdon tube ortubes and the index-shaft are combined means of adjustment, whereby themovement of the tube or tubes may be caused to impart the properrelative motion to the index.

The nature of my invention, and manner in which the same is or may becarried into effect, will be readily understood by reference to theaccompanying drawing, in which- Figure l is a plan of a steam-gage, madein accordance with my invention, with the dial removed. Fig. 2 is aperspective view of the links and the connecting-rod which unites themwith the angle-lever that carries the rack. The remaining figures, from3 to 7, inclusive, are diagrams in plan, representing a few of thevarious modiiications of which my invention is susceptible.

In Fig. 1, A B are two branches of a Bourdon tube, secured in case C,and communicating with steam or exhaust pipe D, in the usual way. Forthe purpose of bringing the two free ends of the branches, the oneun'der the other, I strike the branch A on a smaller circle than thebranch B, each branch being slightly more than a half-circle in extent,so as to bring the free end of branch A directly under the like end ofbranch B. To the head of each tube is pivoted, at h or h', a link, a oral, the two links being of equal, or nearly equal, length, and united attheir other ends by a common pivot, b. The two links, under thisarrangement, constitute the sides of an isosceles triangle, of which thepivot b is the apex. On pivot b is mounted a connecting-rod, o, which isformed with a loop, as seen in Fig. 2, to straddle branch A, and at itsouter end is jointed to the arm d of an angle-lever, pivoted at itsbend, c, to the case, and carrying on its other arm a rack, f, whichrests on the pinion of the indicating-pointer g.

The above-descriled arrangement of the links ce enables me to availmyself fully of the upward movements of the heads of the branches of theBourdon tube. For instance, supposing the head of the tube A to be movedupward, the separately-pivoted end of the link a of this head would movetoward the corresponding end of the other link, and the position of the-apeX or point I) would consequently change, and it would move upwardly'in the arc of a circle, having a radius, al, and a center, h. If, on theother hand, the head of tube B should move upward, then the pivot bwould move in a corresponding direction in the are of a circle, of whicha would be the radius, and h the center. As a matter of fact, however,when pressure is applied to the gage, the two tubes will movesimultaneously, and, therefore, the movement of the pivot b will beupward, and in a path, and for a distance the resultant of the conjoinedmovements of the two.

I have here considered only the effect of the upward movement of thetubes. For practice, they expand outwardly away from each other, as wellas upwardly, and this outward movement of the two has also its effectupon the links, to cause their pivot b to rise, so that, in reality, themovement of the point b depends upon and is the resultant of the outwardexpansion, as well as the upward rising, of the heads or free ends ofthe tubes. It will, of course, be understood that a reverse movement ofthe links takes place when the gage is used to indicate vacuum insteadof pressure, but the principle of action remains unchanged. The movementof the pivotal pin 'or point b is communicated to the rack through theintermediaries hereinbefore named, as will be understood without furtherexplanation.

lllhe adjustment of the gage can be effected by bringing the pivots h lanearer together or farther apart, as desired, this being provided for byjointing the links to pins i', which slide in sockets in the heads ofthe tubes, and are held in place by set-screwsj; or the adjustment maybe effected by making the arm d of the angle-lever in two parts, the oneslotted longitudinally and united by set-screws with the other, asindicated in Fig. l, so that the working length of the arm may beincreased or decreased, as desired.

In Fig. 3 I have represented the manner in which the same e'ect may beobtained from two semicircular tubes struck with the same radius, andwith their heads placed end to end. The arrangement of links,connectionrod, lever, and rack is the same as in Fig. l, except that thehead of one of the tubes B is provided with a sliding pin, i', ofconsiderable length, in order to obtain the needed spreading apart ofthe pivots h h.

Fig. 4 represents substantially the same arrangement ofthe links andconnecting-rod, adapted to a toothed segment-rack, E, pivoted Vmountedon pivot b.

at l to the case, and formed on the other side of the pivot with anadjustable and extensible arm, 2, similar to the arm b of theangle-lever in Fig. l, to the outer end of which the connecting-rod c ispivoted.

In Fig. 5 an arrangement is represented whereby I dispense with theconnecting-rod c, by employing a curvedrack, 3, which rests on thepinion of the index-shaft, and is prolonged into a curved arm, 4, loopedor divided, like the rod c, to straddle the pressure-tube, and Thisarrangement is very simple, but none the less effective.

In Fig. 6, the gage represented in the diagram has but a single tube. Inorder to adapt the links to this gage one of them, a, is pivoted at h,as before, to the head of the gage. The other, al, has its pivotal pointh on the case ofthe gage. The two points 7L h should, of course, be soarranged that they may be brought nearer together or spread apart, andconsequently pivot h may be on a sliding rod, i, in the head of thetube; or the pivot h may be on a bracket adjustable on the gage. The twolinks are pivoted together, as before, at b, which is also the pivot ofconnecting-rod 5, joined to a toothed segment-lever midway between therack or toothed face of said lever and the point 6, where it is pivotedto the case of the gage. Under this arrangement, as a tube constitutingnearly Aa full circle is employed, the links and rod connecting the samewith the rack are arranged within the space inclosed by the tube.

In Fig 7 there is but a single tube, struck on a half circle, orslightly' exceeding a halfcirclc. In this arrangement I employ verynearly the same arrangement of links as shown in the preceding diagram,link a being pivoted at 7L to the tube, and link al at lo to anadjustable bracketon the case of thegage; but while the link al serves,as before, in conjunction with link a, to regulate and control themovement of the pivot I), it also serves as an intermediary tocommunicate the movement to the rack, Vand for this purpose is prolongedbeyond pivot h into an angle-arm, a2, which is jointed to and carriesthe rack. This arm a2 is, like arm d in Fig. 1, divided and adjustable.The link thus becomes, in effect, an angle-lever to actuate or transmitmovement to the rack.

In all the modiiications represented, it will be seen that there is theone feature common to all, of two links jointed together at one end,with their other ends spread apart and pivoted separately, one at leastof said ends being pivoted to the Bourdon tube, and connected, throughtheir common pivotal point, with mechanism to operate the index-shaft ofthe gage, said mechanism, deriving its movement from the changes inposition of' said common pivotal point; and in all the modiiications thevertical movement, as well as the lateral or horizontal movement, of thetube or tubes is fully utilized. In lieu of jointing together the twolinks at `the apex, these ends of the links of Ways in which theinvention can be applied.

may be solidly united, the two thus forming, in effect, a solid V-link,the legs of which are separately pivoted, as before described.

Other modifications might be suggested, but the above are sufficient toindicate the variety What I claim as my invention, and desire to secureby Letters Patent, is-

In a pressure or vacuum gage, the means herein described for operatingthe index-shaft by both the upward or vertical as Well as the horizontalmovement of the Bourdon tube or tubes, the same consisting of two linksjoined @IUT

